This invention relates polymers and said polymers are particularly suited to use in ophthalmic lenses such as contact lenses, intraocular lenses and artificial corneas.
Conventionally, polymers obtained by copolymerizing monomers having silicon groups and hydrophilic monomers have been used as polymers for ophthalmic lenses.
For example, polymers are known that are obtained by copolymerizing 3-tris (trimethylsiloxy) silyl propyl methacrylate with N,N-dimethyl acrylamide. Although these polymers have the merit of high oxygen permeability, they have a high modulus of elasticity, for which reason there is the drawback, for example, that they feel uncomfortable when they are used for contact lenses.
Further, polymers are known that are obtained by copolymerizing siloxanyl monomers represented by the formula below with N,N-dimethyl acrylamide. Although these polymers have a low modulus of elasticity, they have the drawback of poor oxygen permeability. 
This invention has the objective of providing polymers of high oxygen permeability and a low modulus of elasticity and ophthalmic lenses and contact lenses in which they are used.
In order to achieve this objective, this invention has the structure described below.
They are polymers characterized in that they are obtained by copolymerizing 5 to 90 parts by weight of a monomer represented by the formula below (hereafter referred to as SiMAA), 5 to 90 parts by weight of 3-tris (trimethylsiloxy) silyl propyl methacrylate (hereafter referred to as TRIS), 5 to 70 parts by weight of N,N-dimethyl acrylamide (hereafter referred to as DMAA) and 0.1 to 3 parts by weight of monomer having two or more copolymerizable carbon-carbon unsaturated bonds in 1 molecule (provided that the total quantity of SiMAA, TRIS and DMAA is 100 parts by weight and that the total quantity of SiMAA and TRIS is 30 to 95 parts by weight). 